The present invention relates to a multiplexing technique and, more particularly, to a packet multiplexing technique of multiplexing packets and transferring a multiplexed packet.
The IP (Internet Protocol) which has been spread widely among computer networks transfers an Internet diagram from a transmission source host to a destination host but does not support sequencing or flow control. This protocol also transfers data in a size complying with a request from a host application.
The LTE (Long Term Evolution) communication technique which is defined by 3GPP (3rd Generation Partnership Project) as one of high-speed data communication specifications for portable phones has suggested to transfer a user IP packet having the above-described characteristic via a logical transmission path formed by tunneling using GTP-U (GPRS Tunneling Protocol for User plane) (concerning LTE, see “3GPP TS36.300 v8.1.0 2007-07-17, Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 (Release 8)”, and concerning GTP-U, see “3GPP TS29.060 v8.0.0 2007-06-22, 3GPP; Technical Specification Group Core Network and Terminals; General Packet Radio Service (GPRS); GPRS Tunneling Protocol (GTP), across the Gn and Gp interface (Release 8)”). There is also suggested to use VoIP to transfer a CS (Circuit Switch) call used as a voice communication system in 3GPP (from rel'99).
In, e.g., a voice codec of AMR (Advanced Multi Rate) scheme, user data of 12.2 kbps has a payload length of 31 bytes (40 bytes when the header and the like are taken into consideration) at an interval of 20 ms. For this reason, when transferring packets of a service which uses a narrow band but is time critical (ensures real-time processing), like VoIP, an enormous number of small-sized packets are delivered on an S1/X2 interface in accordance with the number of users. This may increase the process load of each node or degrade the transmission efficiency of the network due to overhead of IP/UDP headers.
That is, when a communication system for multiplexing user IP packets and transferring a multiplexed packet, like the S1/X2 interface of the LTE communication technique, is applied to a broadband IP network, and a lot of small packets are transferred, as in VoIP, overhead of headers degrades the transmission efficiency.
Against this backdrop, protocols for CIP (Channel Interface Processor) and MPLS (Multi-Protocol Label Switching) have been proposed as methods of multiplexing small-size IP packets in 3GPP (concerning CIP and MPLS, see “3GPP TS25.933 v5.4.0 2004-01-13, Technical Specification Group Radio Access Network; IP transport in UTRAN (Release 5)”).